Workpiece coatings can be applied in many different ways. In some instances, a coating material is supplied within a chamber, usually a vacuum chamber, through a sprayer that accelerates the coating vapor and deposits it onto one or more workpieces positioned within the chamber. Alternatively, the coating material may be evaporated from a pool of material, filling the deposition chamber and condensing onto the workpieces. In other instances, the coating material may be atomized to create an aerosol that condenses onto the workpieces. Condensation of the coating material can be accomplished by various methods, for example, by physical methods or chemical methods. In a typical configuration, one or more nozzles or outlets for the coating material are positioned within the chamber, and the workpieces are rotated in front of the nozzles while the nozzles are operating to achieve a uniform deposition coating on each workpiece.
One known device for coating a plurality of workpieces is described in U.S. Pat. No. 6,761,772, issued to Giacri at al. on Jul. 13, 2004 (hereafter the '772 patent). The '772 patent describes a device that supports and rotates eight (8) workpieces simultaneously during a coating process. The workpieces are rotatably mounted at the edge of a turntable that is connected to a drive shaft. As the turntable rotates, a finger engages a tooth formed on a drive wheel that lies beneath each workpiece. This engagement operates to incrementally rotate each workpiece as it passes in front of the finger, exposing an incrementally new profile of the workpiece to the vapor emanating from a respective nozzle. The disclosure of the '772 patent describes that the finger is connected to an extension of a rotating ring which is mounted on the turntable itself. The rotating ring is connected to the turntable such that the two components can rotate with respect to each other, but are also connected to each other. The extension is arranged to cooperate with a rod serving as a stop, in such a way that rotation of the driving device together with the turntable is prevented.
One disadvantage of the device disclosed in the '772 patent is the relatively large frictional interface between the rotating ring and the turntable. Because of operation of the device in an environment where large amounts of coating material are present, any deposition of coating material within the interface between the turntable and the ring that is attached thereto may cause an increase in friction between the two components, which in turn places a larger burden in the actuator that acts to rotate the turntable. Further, the peripheral interface between the rotating ring and the turntable is near the source of coating material in that the coating material is sprayed onto the workpieces from above and off the side of the assembly. Moreover, the disclosed device is limited to providing two degrees of compounded rotation inasmuch as the rotation of the turntable is compounded with the incremental rotation of each of the workpieces.